1. Field of the Invention
The present invention generally relates to a device for the electroplating and fabrication of electronic devices and components and in particular, relates to a plating bath device for use in the semiconductor industry to plate various metals onto substrates suspended in a liquid having laminar flow.
2. Description of Related Art
A substrate must be coated with certain metals in order to accommodate etching and photoresist lift off for integrated circuits and the like on the substrate. These various metals may be deposited using a number of techniques, such as electron beam evaporation or electroplating.
Electroplating is commonly used in the electronics industry. Since a great number of electronic devices are manufactured using lithographic (photoresist) processes to reproduce patterns on substrates, it is highly desirable to achieve a consistent layer distributed across an entire substrate, and to repeat this consistency from substrate to substrate. In other words, to achieve a high precision image transfer, profiles across the substrate must be uniform in line width and depth.
A disadvantage associated with prior art techniques is that of relatively uneven flow of the fluid of an electroplating tank. This fluid, commonly referred to as electroplating solution, is circulated about a predetermined path in the prior art in an attempt to maintain uniformity in the deposited materials. The frequency of the electroplating solution passing over a given portion of a substrate determines deposition rate and uniformity across the substrate.
In electroplating processes one must use strong solution agitation to ensure electrochemical reaction. However, the strong agitation hinders the deposition uniformity effect across the substrate. This dilemma is not suitably resolved by the any of the prior art.
One prior art device utilizes a propeller to drive the electroplating fluid and a complex baffling system to attempt to transform the turbulent fluid stream into a laminar flow stream. Another prior art device consists of a commercial embodiment of a device in which a silicon substrate is placed upside down in a bath and a fountain of electroplating solution flows up against the substrate to plate it. In additional to being cost prohibitive, this splashing method fails to adequately provide a consistent and accurate plating thickness across the surface of a semiconductor substrate. Thus, a problem has existed in the prior art for a plating bath which provides a uniform fluid flow of the electroplating solution during electroplating of a substrate.